Synergistic Ru/Co-S bonded single-atom and nanoparticle catalysts for high-performance bifunctional oxygen electrocatalysis in rechargeable zinc-air batteries

The development of efficient and sustainable energy conversion and storage technologies is the focus of modern scientific and technological research. This study doped Ru single atoms into a zinc zeolite imidazole framework (Ru-ZIF-8), followed by the adsorption of Co nanoparticles at the interface for the first pyrolysis and the introduction of S for the second pyrolysis to obtain a composite bifunctional electrocatalyst composed of Ru single atoms and Co nanoparticles (Co@Ru-SAs-HSNC), with Ru/Co-S coordination and stable anchoring on a hollow N-doped carbon substrate. The theoretical calculation results revealed that the introduction of S atoms to replace N atoms and form Ru sites provided a greater driving force for the reaction, regulated the electronic structure, and slowed the deactivation of the sintering of the metal particles. The secondary pyrolysis could produce more active sites for the catalyst and form a more uniform and stable pore structure, improving the activity and stability of the catalyst. In an alkaline environment, Co@Ru-SAs-HSNC exhibited a high half-wave potential of 0.90 V in the oxygen reduction reaction (ORR) and a low overpotential of 278 mV at 50 mA cm⁻² in the oxygen evolution reaction (OER). Additionally, Co@Ru-SAs-HSNC was used as the positive electrode of a rechargeable zinc-air battery, achieving a 205 mW cm⁻² peak power density. As shown in the long-term constant-current charge–discharge tests, Co@Ru-SAs-HSNC had a cycle time of up to 1134 h with high round-trip efficiency.